2.3.2 Initial visibility

When Emacs first visits an Org file, the global state is set to OVERVIEW,
i.e., only the top level headlines are visible1. This can be configured through the variable
org-startup-folded, or on a per-file basis by adding one of the
following lines anywhere in the buffer:

Furthermore, any entries with a ‘VISIBILITY’ property (see Properties and columns) will get their visibility adapted accordingly. Allowed values
for this property are folded, children, content, and
all.

C-u C-u <TAB> (org-set-startup-visibility)

Switch back to the startup visibility of the buffer, i.e., whatever is
requested by startup options and ‘VISIBILITY’ properties in individual
entries.

Footnotes

[1] When
org-agenda-inhibit-startup is non-nil, Org will not honor the default
visibility state when first opening a file for the agenda (see Speeding up your agendas).